S.B. Nielsen

A transient divided-bar method for simultaneous measurements of thermal conductivity and thermal diffusivity

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Accurate information on thermal conductivity and thermal diffusivity of materials is of central importance in
relation to geoscience and engineering problems involving the transfer of heat. Within the geosciences, this
applies to all aspects regarding the determination of terrestrial heat flow and subsurface temperature modelling.
Several methods, including the classical divided-bar technique, are available for laboratory measurements of
thermal conductivity, and much fewer for thermal diffusivity. We have generalized the divided-bar technique to the
transient case, in which thermal conductivity and volumetric heat capacity, and thereby also thermal diffusivity,
are measured simultaneously. As the density of samples is easily determined independently, specific heat capacity
may also be determined. Finite element formulation provides a flexible forward solution for heat transfer across
the bar and thermal properties are estimated by inverse Monte Carlo modelling. This methodology enables a
proper quantification of experimental uncertainties on measured thermal properties.
The developed methodology was applied to laboratory measurements of various materials, including a standard
ceramic material and different rock samples, and measuring results were compared with results applying traditional
steady-state divided-bar and an independent line-source method. All measurements show highly consistent
results and with excellent reproducibility and high accuracy. For conductivity, uncertainty is typically 1-3 %, and
for diffusivity uncertainty may be reduced to about 3-5 %. The main uncertainty originates from the presence of
thermal contact resistance associated with the internal interfaces of the bar. They are not resolved during inversion,
and it is highly important that they are minimized by careful sample preparation.
Original languageEnglish
JournalGeophysical Research Abstracts
VolumeVol. 18
IssueEGU2016-12141
Number of pages1
ISSN1607-7962
Publication statusPublished - 2016
EventEuropean Geosciences Union General Assembly 2016 -
Duration: 17 Apr 201622 Apr 2016

Conference

ConferenceEuropean Geosciences Union General Assembly 2016
Period17/04/201622/04/2016

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